Tube Amp Component ID and upgrade help?

Discussion in 'DIY (Do-It-Yourself) Discussions' started by ostewart, Jun 17, 2017.

  1. ostewart
    Hi Guys,

    Had my Feliks Audio Espressivo for about 2 years now, took it apart yesterday to see what's inside and can any of you recommend upgrades for any of the parts below:

    Thinking about getting nichicon caps, the rest I don't know though.

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    Last edited: Jun 17, 2017
  2. Sodacose
    Got a schematic of the amp?

    I don't mind orange drop caps for audio and use them regularly where it makes sense. I even use them for interstage coupling and haven't ever felt like they are a bottleneck. For the 3.3uF, I like the Cornell Dubilier 940C series, but I think they are rated at 600V+ so a 3.3uF is going to be pretty big. I've also used Fast Caps and Dayton poly caps for this kind of thing. Both are fine options.

    Depending on what the big electrolytic is doing, you may not see much of a change by swapping it. Try a Nichicon that's rated for 250V and see if it does anything.
     
    Oscar-HiFi likes this.
  3. HiGHFLYiN9
    You're most likely going to run into real-estate issues with the caps. As Sodacose mentioned, increasing the quality of the film caps generally means they are going to be larger. For the electrolytics, there aren't really any audiophile options at 250v (e.g. Silmic II, Nichicon Muse/Fine Gold, etc.) aside from perhaps Mundorf. You might be able to find a Nichicon "for audio" cap in that value, but I doubt there will be an audible difference. The Mundorfs are really pricey, not really worth it in this application. Also, given that the PCB is single-sided, you'll want to be especially careful when reworking or you could end up pulling off a trace or two. For any resistors in the signal path, Kiwame carbon film (Koa Speers 2W at Mouser) are my personal favorite, but there are plenty of options out there.
     
    Oscar-HiFi and Sodacose like this.
  4. Sodacose
    I think the Nichicon FG series only goes up to 100V, at least I've only ever used them as cathode bypass for tubes or in SS circuits. Beyond that I use one of their standard series or whatever is cheap from a reliable brand when needed. I bought a bunch of Nichicon GN series snap-in 120u 500V caps a while ago and have been slowly using them up in larger power supplies. It doesn't look like a snap in will work here either way though.

    Lately I've been using motor run caps in my power supplies. Talk about size constraints :)
     
  5. Oscar-HiFi
    Thanks for the advice, so leave the Samwha ones, the amp has quite a bit of space in it, so replacing the JB ones should be fairly easy, but I'm still unsure whether it'll make any real difference.

    It's not an expensive amp, but its great for the price, and yeah lifting a trace could be an issue. Are there any other areas in the amp to look at upgrading?

    I have some iFi Audio 5670 tubes in adapters to fit 6922 sockets, and there is a grounding issue with them, that does not happen when using 6922 valves. iFi have been really helpful trying to trouble shoot, but it is very odd as it's only happening on one channel of the amp. I opened the amp up to see if there were any obvious signs of bad joints that could be the cause, but nothing that I could see.

    anything I should be looking for to detect the grounding issue?
     
  6. HiGHFLYiN9
    Of those I prefer the Mundorf Supreme followed by the Obbligato. I've used the CC SA and ESA, and they are good too, but not as good imho. I've read the Mundorf MKP is a little grainy and not even as good as a Solen so I have never purchased.

    As far as other upgrades, adding a choke to the power supply might be a nice cheap upgrade.
     
    Last edited: Jun 22, 2017 at 2:26 PM
    ostewart likes this.

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